/*
 * Created on Oct 08, 2004
 * Created by Alon Rohter
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */
package com.aelitis.azureus.core.util.average;

import org.gudy.azureus2.core3.util.SimpleTimer;
import org.gudy.azureus2.core3.util.SimpleTimer.TimerTickReceiver;
import org.gudy.azureus2.core3.util.SystemTime;

import com.aelitis.azureus.core.util.GeneralUtils;

/**
 * Generates different types of averages.
 */
public abstract class AverageFactory {

    /**
     * Create a simple running average.
     */
    public static RunningAverage RunningAverage() {
        return new RunningAverage();
    }

    /**
     * Create a moving average, that moves over the given number of periods.
     */
    public static MovingAverage MovingAverage(int periods) {
        return new MovingAverage(periods);
    }

    /**
     * Create a moving average, that moves over the given number of periods and gives immediate results (i.e. after the first update of X the average
     * will be X
     */

    public static MovingImmediateAverage MovingImmediateAverage(int periods) {
        return new MovingImmediateAverage(periods);
    }

    /**
     * Create an exponential moving average, smoothing over the given number of periods, using a default smoothing weight value of 2/(1 + periods).
     */
    public static ExponentialMovingAverage ExponentialMovingAverage(int periods) {
        return new ExponentialMovingAverage(periods);
    }

    /**
     * Create an exponential moving average, with the given smoothing weight. Larger weigths (closer to 1.0) will give more influence to recent data
     * and smaller weights (closer to 0.00) will provide smoother averaging (give more influence to older data).
     */
    public static ExponentialMovingAverage ExponentialMovingAverage(float weight) {
        return new ExponentialMovingAverage(weight);
    }

    /**
     * Creates an auto-updating immediate moving average that will auto-deactivate average maintenance when values are not being extracted from it,
     * auto-reactivate when required etc.
     * 
     * @param periods
     * @param adapter
     * @param instance
     * @return
     */

    public static <T> long LazySmoothMovingImmediateAverage(final LazyMovingImmediateAverageAdapter<T> adapter, final T instance) {
        int update_window = GeneralUtils.getSmoothUpdateWindow();
        int update_interval = GeneralUtils.getSmoothUpdateInterval();

        return (LazyMovingImmediateAverage(update_window / update_interval, update_interval, adapter, instance));
    }

    public static <T> long LazyMovingImmediateAverage(final int periods, final int interval_secs,
            final LazyMovingImmediateAverageAdapter<T> adapter, final T instance) {
        LazyMovingImmediateAverageState current = adapter.getCurrent(instance);

        if (current == null) {

            final LazyMovingImmediateAverageState state = current = new LazyMovingImmediateAverageState();

            SimpleTimer.addTickReceiver(new TimerTickReceiver() {

                public void tick(long mono_now, int tick_count) {
                    long now = SystemTime.getMonotonousTime();

                    if (now - state.last_read > 60 * 1000) {

                        SimpleTimer.removeTickReceiver(this);

                        adapter.setCurrent(instance, null);

                    } else if (tick_count % interval_secs == 0) {

                        long value = adapter.getValue(instance);

                        long last = state.last_value;
                        long diff = value - last;

                        if (last >= 0 && diff >= 0) {

                            MovingImmediateAverage average = state.average;

                            if (diff == 0) {

                                state.consec_zeros++;

                            } else {

                                state.consec_zeros = 0;
                            }

                            if (average == null) {

                                if (diff > 0) {

                                    state.average = average = MovingImmediateAverage(periods);

                                    int zeros_to_do = Math.min(state.consec_zeros, periods);

                                    for (int i = 0; i < zeros_to_do; i++) {

                                        average.update(0);
                                    }
                                }
                            }

                            if (average != null) {

                                long ave = (long) average.update(diff);

                                if (ave == 0 && average.getSampleCount() >= periods) {

                                    // looks pretty dead

                                    state.average = null;
                                }
                            }
                        }

                        state.last_value = value;
                    }
                }
            });

            adapter.setCurrent(instance, current);

        } else {

            current.last_read = SystemTime.getMonotonousTime();
        }

        MovingImmediateAverage average = current.average;

        if (average == null) {

            return (0);

        } else {

            return ((long) average.getAverage() / interval_secs);
        }
    }

    public interface LazyMovingImmediateAverageAdapter<T> {
        public LazyMovingImmediateAverageState getCurrent(T instance);

        public void setCurrent(T instance, LazyMovingImmediateAverageState average);

        public long getValue(T instance);
    }

    public static class LazyMovingImmediateAverageState {
        private MovingImmediateAverage average;
        private int consec_zeros;
        private long last_value = -1;
        private long last_read = SystemTime.getMonotonousTime();
    }
}
